Question 936988
{{{ 8^r = 4^t }}}
{{{ ( 2^3 )^r = ( 2^2 )^t }}}
Use the rule that says:
{{{ ( a^b )^c = a^(b*c) }}}
{{{ 2^(3r) = 2^(2t) }}}
{{{ 3r = 2t }}}
{{{ r/t = 2/3 }}}
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check:
Take the {{{t}}}th root of both sides 
of the problem
{{{ 8^(r/t) = 4^(t/t) }}}
{{{ 8^(2/3) = 4 }}}
{{{ ( 2^3 )^(2/3) = 4 }}}
{{{ 2^2 = 4 }}}
{{{ 4 = 4 }}}
OK